Snowmobile

ABSTRACT

A snowmobile including a chassis, shell, and an engine. The shell may be fixed to a front portion of the chassis and extend away from the chassis in a forward direction. The shell may be disposed forward of the steering axis. The shell may define a chamber that fluidly communicates with the engine via a flexible coupling interposed between the shell and the engine.

RELATED APPLICATIONS

This is a Continuation of application Ser. No. 10/236,607 filed Sep. 6,2002 now U.S. Pat. No. 6,796,395.

This application is related to and claims priority to U.S. ProvisionalApplication No. 60/318,151, filed Sep. 7, 2001, and entitled SnowmobileDrivetrain.

This application is also related to and claims priority to U.S.Provisional Application No. 60/317,892, filed Sep. 7, 2001, and entitledSnowmobile Providing an Enhanced Riding Experience.

The entire disclosures of the above mentioned applications are herebyincorporated by reference in their entirety.

FIELD OF THE INVENTION

The present invention relates generally to snowmobiles. Moreparticularly, the present invention relates to the human-to-machineinterface of a snowmobile.

BACKGROUND OF THE INVENTION

Since their development in the middle of the 20^(th) century,snowmobiles have gained widespread popularity. Snowmobiles are commonlyused for trail riding and utility applications. Perhaps the most commonsnowmobile application is recreational trail riding. Trail riding on asnowmobile allows a snowmobile enthusiast to travel through areas whichare not accessible by other types of vehicles. For example, snowmobilescan travel very rapidly across frozen lakes during the winter innorthern climates. Modern snowmobiles, can cover ground very rapidly andcan cover great distances. Frequently, snowmobile enthusiasts ride theirsnowmobile for many hours straight and cover many miles.

A rider operates a snowmobile by providing inputs such as accelerationinputs provided using a throttle, deceleration inputs provided using abrake, and steering inputs provided using a set of handle bars. Therider may also influence the performance of the machine by shifting hisor her weight, for example, by leaning into a turn.

Frequently, people become interested in snowmobiling because of theunique riding experience that snowmobiles provide. Part of the thrill ofriding a snowmobile is encountering challenging terrain, and traversingthat terrain through a combination of the skill of the rider and the waythat the snowmobile reacts to the inputs provided by the rider. Aspectsof a snowmobile such as the overall weight of the snowmobile, the weightdistribution of the snowmobile, and the location of the snowmobilecenter of gravity all effect the riding experience enjoyed by asnowmobiling enthusiast.

The ability of a rider to traverse challenging terrain smoothly andquickly frequently depends upon the way that the snowmobile responds tothe rider. As mentioned previously, the rider can control the snowmobileby providing inputs using the handlebar, brake and throttle. The ridercan also control the snowmobile by selectively shifting his or herweight.

The way that a particular snowmobile responds to inputs provided by arider may depend upon the snowmobile's total inertia, the snowmobile'smoment of inertia, and the location of the snowmobile's center ofgravity. The total inertia of a snowmobile has an effect on thatsnowmobile's performance because this total inertia determines theextent to which the snowmobile will resist changes in location andlinear velocity. For example, the inertia of an overly heavy snowmobilemay limit how rapidly that snowmobile can accelerate and decelerate. Themoment of inertia of a snowmobile also has an effect on thatsnowmobile's performance, since it determines the extent to which thesnowmobile will resists changes in angular position and rotationalvelocity. The moment of inertia of a snowmobile is determine, at leastin part by the total mass of the snowmobile the way in which that massis distributed.

SUMMARY OF THE INVENTION

The present invention relates generally to snowmobiles providing anenhanced riding experience. More particularly, the present inventionrelates to the human-to-machine interface of a snowmobile. A snowmobilein accordance with the present invention may include a frame defining atunnel and a drive track rotatably supported within the tunnel. Thesnowmobile may also include an engine connected to the frame andoperatively coupled to the drive track by a drivetrain.

A seat may be fixed to the frame for receiving a rider of thesnowmobile. A pair of handle bars may be rotatably coupled to the frameand adapted to receive the hands of the rider. A pair of floor boardsmay be fixed to the frame and adapted to receive the feet of the rider.In some embodiments, the floor boards include toe stops.

In one aspect of the invention, the engine includes a cylinder borehaving a cylinder bore axis that is directed rearwardly and upwardly sothat a center of mass of the engine is disposed rearward of a center ofrotation of a crank shaft of the engine. Placing the engine in thisposition may provide a snowmobile having a lower polar moment of inertiacompared to a snowmobile having an engine with a center of masspositioned directly above, or in front of the rotational center of thecrankshaft.

The engine of the snowmobile has a first side extending in a firstdirection from the cylinder bore axis and a second side extending in asecond direction from the cylinder bore axis. In one advantageous aspectof the present invention, air may enter the cylinder bore from the firstside of the engine, and exhaust gases may exit the engine from the sameside. In some applications, this arrangement may facilitating placingthe fuel tank in close proximity to the cylinder of the engine.

In still another aspect of the present invention, the fuel tank has afront wall that is generally sloped rearwardly and upwardly. In someimplementations of the present invention, the sloped wall of thesnowmobile is generally parallel to the cylinder bore axis of theengine. In some implementations, the fuel tank and the engine may bepositioned in such close proximity to one another, that a lateralreference plane passing through the snowmobile intersects both the fueltank and the cylinder of the engine.

In an additional aspect of the invention, a starter of the snowmobile isdisposed between the engine and the centroid of the snowmobile. Placingthe starter in this position provides a snowmobile having a lower polarmoment of inertia compared to a snowmobile having the starter disposedon a front side of the engine.

A snowmobile in accordance with the present invention may comprise achassis, a shell fixed to a front portion the chassis and extending awayfrom the chassis in a forward direction, and an engine coupled to thechassis for propelling the snowmobile. In some implementations, theshell defines a chamber fluidly communicating with the engine via aflexible coupling interposed between the shell and the engine.

In some implementations, the snowmobile also includes at least one skicoupled to the chassis by a suspension so that the ski is pivotableabout a steering axis. In these implementations, the shell may beadvantageously disposed forward of the steering axis.

In some implementations, the snowmobile includes a hood that isrotatably supported by the shell. In these implementations, a plenumdefined by the hood advantageously fluidly communicates with the chamberdefined by the shell at least when the hood is in a closed position. Insome implementations, the chamber defined by the shell may be accessedvia an opening in the shell when the hood is in the open position.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a snowmobile in accordance with anexemplary embodiment of the present invention.

FIG. 2 is a perspective view of three exemplary bodies disposed along anaxis.

FIG. 3 is a diagrammatic plan view of a snowmobile in accordance with anexemplary embodiment of the present invention.

FIG. 4 is a perspective view of an assembly in accordance with anexemplary embodiment of the present invention.

FIG. 5 is an additional perspective view of the assembly of FIG. 4.

FIG. 6 is an additional perspective view of the assembly of FIG. 4.

FIG. 7 is yet another perspective view of the assembly of FIG. 4.

FIG. 8 is still another perspective view of the assembly of FIG. 4.

FIG. 9 is a plan view of a snowmobile and a rider.

FIG. 10 is a plan view of a snowmobile and a rider.

FIG. 11 is a plan view of a snowmobile and a rider.

FIG. 12 is a plan view of a snowmobile and a rider.

FIG. 13 is a perspective view of an assembly in accordance with anexemplary embodiment of the present invention.

FIG. 14 is a perspective view of an assembly in accordance with anexemplary embodiment of the present invention.

FIG. 15 is a plan view of a snowmobile in accordance with an exemplaryembodiment of the present invention.

FIG. 16 is a plan view of a snowmobile in accordance with the presentinvention.

FIG. 17 is a perspective view of an assembly in accordance with anexemplary embodiment of the present invention.

FIG. 18 is a perspective view of an assembly including frame of theprevious figure and a lightweight shell that is preferably fixed to afront portion of frame.

FIG. 19 is a perspective view of an assembly including frame andlightweight shell shown in the previous figure.

FIG. 20 is a cut away perspective view of an assembly includinglightweight shell and hood shown in the previous figure.

FIG. 21 is a plan view of an assembly including a lightweight shell inaccordance with an exemplary embodiment of the present invention.

FIG. 22 is a cross sectional view of an assembly including a lightweightshell in accordance with an exemplary embodiment of the presentinvention.

FIG. 23 is an additional cross sectional view of the assembly of theprevious figure.

FIG. 24 is an additional plan view of snowmobile.

FIG. 25 is a perspective view of a handle bar assembly including ahandlebar that is coupled to a shaft.

FIG. 26 is a table of standing body dimensions that appears inMIL-STD-1472C.

FIG. 27 is an illustration of standing body dimensions that correspondsto the table in FIG. 26.

DETAILED DESCRIPTION

The following detailed description should be read with reference to thedrawings, in which like elements in different drawings are numberedidentically. The drawings, which are not necessarily to scale,depictpre-selected embodiments and are not intended to limit the scopeof the invention. Examples of constructions, materials, dimensions, andmanufacturing processes are provided forpre-selected elements. All otherelements employ that which is known to those of skill in the field ofthe invention. Those skilled in the art will recognize that many of theexamples provided have suitable alternatives that can be utilized.

FIG. 1 is a perspective view of a snowmobile 40 in accordance with anexemplary embodiment of the present invention. In FIG. 1, a yaw axis102A, a pitch axis 102B, and a roll axis 102C are all shown intersectinga center of gravity 104 of snowmobile 40. Snowmobile 40 has a polarmoment of inertia (PMI) about each of these axes. In a preferredembodiment of the present invention, a rider of snowmobile 40 may createor change a moment about pitch axis 102B by altering the distribution ofhis or her weight. For example, a moment created about pitch axis 102Bby the asymmetrical application of the riders weight may be used tocause the snowmobile to assume climbing attitude or a diving attitude.When this is the case, the moment created by the rider must overcome thepolar moment of inertia (PMI) of snowmobile 40 about pitch axis 102B.The level of resistance of snowmobile 40 to reacting to such a momentwill be generally proportional to the polar moment of inertia ofsnowmobile 40.

A snowmobile in accordance with the present invention may beparticularly well suited for extreme riding conditions. Examples ofextreme riding conditions may include, for example, snocross racing,riding in alpine conditions, riding in deep snow, hill climbing, andwater skipping. In some extreme riding conditions, it may be desirablefor the rider to control the attitude of snowmobile 40 by changingdriving postures.

FIG. 2 is a perspective view of three exemplary bodies disposed along anaxis 102. Moment of inertia may be illustrated with reference to FIG. 2.In FIG. 2, each of the bodies A, B, C has a mass of M. In FIG. 2 it maybe appreciated that although the three bodies A, B, C have the samemass, the mass is distributed differently about axis 102. Because thedistribution of the mass is different, these three bodies have differentmoments of inertia about axis 102. More particularly, the moment ofinertia of body A is less than the moment of inertia of body B, and themoment of inertia of body C is greater than that of body B.

A snowmobile typically includes a number of components. Some of thesecomponents have a relatively high density while others have a relativelylow density. In some embodiments of the present invention, a snowmobileis provided in which relatively lightweight components are placed at theextreme ends of the snowmobile, thus enabling components having arelatively high density to located in close proximity to the geometriccenter of the snowmobile and/or the centroid of the snowmobile. Forexample, in some exemplary embodiments, a lightweight shell is disposedat the extreme front end of a snowmobile in accordance with the presentinvention.

FIG. 3 is a diagrammatic plan view of a snowmobile 100 in accordancewith an exemplary embodiment of the present invention. In FIG. 3 it maybe appreciated that snowmobile 100 includes an engine 106 that isoperatively coupled to a drive track 108 by a drivetrain 120. In theembodiment of FIG. 3, drive track 108 of snowmobile 100 is partiallydisposed within a tunnel 122 defined by a frame 124 of snowmobile 100.Drive track 108 may be used to propel snowmobile 100.

In the embodiment of FIG. 3, a throttle body 126 is fluidly coupled toengine 106. Air entering engine 106 may flow through throttle body 126.Throttle body 126 is coupled to an air box 128. Air box 128 may includefilter media for filtering incoming air. Air box 128 is fluidly coupledto an air plenum 130 defined by a hood 132 of snowmobile 100. Air plenum130 is preferably configured such that air is drawn from an areaproximate the rider of snowmobile 100 and directed to air box 128.

In the embodiment of FIG. 3, a starter 134 is disposed behind and nearthe bottom of engine 106. Engine 106 of snowmobile 100 includes acylinder block 136 defining a cylinder bore 138 having a cylinder boreaxis 166. Cylinder block 136 also defines an air inlet port 140 and anexhaust port 142.

Air may enter cylinder bore 138 via air plenum 130, air box 128,throttle body 126 and inlet port 144. Exhaust gases may exit cylinderbore 138 via exhaust port 142 and an exhaust pipe 148 which fluidlycommunicates with exhaust port 142. In the embodiment of FIG. 3, airinlet port 140 and exhaust port 142 are both disposed on a front side ofcylinder bore axis 166. Also in the embodiment of FIG. 3, a heat shield146 is disposed between air inlet port 140 and exhaust port 142. In FIG.3 it may be appreciated that a heat shield 146 is dimensioned so that itextends between throttle body 126 and exhaust pipe 148.

The human-to-machine interface of snowmobile 100 includes a handlebar150, a seat 152, a pair of running boards 154, and a pair of toe stops156. The operator of snowmobile 100 may control the snowmobile byapplying forces to handlebar 150, seat 152, running boards 154, and toestops 156. The operator of snowmobile 100 may also control thesnowmobile by assuming various postures in which the operators weight isdistributed over handlebar 150, running boards 154, toe stops 156, andseat 152 in varying degrees. In the embodiment of FIG. 3, toe stops 156intersect running boards 154 at an intersection 158.

In the embodiment of FIG. 3, handlebar 150 rotates about a steering axis168. Snowmobile 100 has a control point 160 that is defined by steeringaxis 168 and a grip plane 162. In the embodiment of FIG. 3, grip plane162 is defined by a first grip axis and a second grip axis. In someembodiments of the present invention, handlebar 150 may be moveablebetween a first position and a second position with steering axis 168and grip plane 162 defining control point 160 when handlebar 150 is inthe first position, and with steering axis 168 and grip plane 162defining second control point when handlebar 150 is in the secondposition.

Handlebar 150 is coupled to a steering column 164 that rotates aboutsteering axis 168. In the embodiment of FIG. 3, cylinder bore axis 166and steering axis 168 are generally parallel. A center of gravity 104 ofsnowmobile 100 is also illustrated in FIG. 3. In the embodiment of FIG.3, engine 106 is inclined rearwardly so that the weight of engine 106 isdisposed relatively close to center of gravity 104 of snowmobile 100.

FIG. 4 is a perspective view of an assembly in accordance with anexemplary embodiment of the present invention. The assembly of FIG. 4includes a drivetrain 120 for a snowmobile. In the embodiment of FIG. 4,drivetrain 120 includes a drive clutch 172 that is coupled to a crankshaft 174 of an engine 106. A drive belt 176 is disposed about driveclutch 172 and couples drive clutch 172 to a driven clutch 178. Drivenclutch 178 rotates about a driven clutch axis. Driven clutch 178 isoperably coupled to a drive shaft 180 by a reducer. A drive sprocket 182is coupled to drive shaft 180. Drive shaft 180 and drive sprocket 182rotate about a drive shaft axis. Drive sprocket 182 preferably mateswith a drive track 108. Rotation of drive sprocket 182 causes movementof drive track 108, so that drive track 108 may propel a snowmobile.

The assembly of FIG. 4 also includes a steering column 164, a runningboard 154, and a toe stop 156. The assembly of FIG. 4 preferably alsoincludes a second running board 154 and a second toe stop (not shown inFIG. 4). The operator of a snowmobile including assembly may control thesnowmobile by applying forces to steering column 164, running boards154, and toe stops 156. The operator of the snowmobile may also controlthe snowmobile by assuming various postures in which the distribution ofthe operator's weight is distributed over steering column 164, asnowmobile seat, running boards 154, and toe stops 156.

FIG. 5 is an additional perspective view of the assembly shown in theprevious figure. In FIG. 5 it may be appreciated that the rotationalaxis of the drive clutch 172, the rotational axis of driven clutch 178,and the rotationally axis of a drive shaft 180 define a trihedron 190.In a preferred embodiment of assembly, each side of trihedron 190 has alength that is selected to provide a relatively small polar moment ofinertia (PMI).

FIG. 6 is an additional perspective view of the assembly of FIG. 4. InFIG. 6 it may be appreciated that engine 106, drive clutch 172, drivenclutch 178, and drive shaft 180 are all disposed within an imaginarycylinder 192A centered on a pitch axis 102B of a snowmobile includingthe assembly. In a preferred embodiment, imaginary cylinder 192A has aradius that is selected to provide a relatively small polar moment ofinertia (PMI) about pitch axis 102B. In some embodiments, the assemblymay further include a starter that is disposed behind and near thebottom of engine 106. When this is the case, the starter is preferablydisposed within imaginary cylinder 192A.

FIG. 7 is yet another perspective view of the assembly of FIG. 4. InFIG. 7 it may be appreciated that engine 106, drive clutch 172, drivenclutch 178, drive shaft 180, and drive track 108 are all disposed withinan imaginary cylinder 192B centered on a roll axis 102C of a snowmobileincluding the assembly. In some embodiments of the present invention, afuel tank of the snowmobile may also be disposed within imaginarycylinder 192B. In a preferred embodiment, imaginary cylinder 192B has aradius that is selected to provide a desired polar moment of inertia(PMI) about roll axis 102C.

FIG. 8 is still another perspective view of the assembly of FIG. 4. InFIG. 8, it may be appreciated that engine 106, drive clutch 172, drivenclutch 178, and drive shaft 180 are all disposed within first imaginarycylinder 192A and second imaginary cylinder 192B. In FIG. 8 it may beappreciated that first imaginary cylinder 192A has a first radius RAthat is smaller than a second radius RB of second imaginary cylinder192B. In some applications, a generally low and wide arrangement ofdrive elements provides stability about a roll axis 102C and at the sametime allows a snowmobile rider to easily make adjustments to theattitude of a snowmobile about a pitch axis 102B. In one embodiment ofthe present invention, the radius of first imaginary cylinder 192A andthe radius of second imaginary cylinder 192B are selected so that thepolar moment of inertia of a snowmobile including assembly about pitchaxis 102B is substantially equal to the polar moment of inertia of asnowmobile including assembly about roll axis 102C.

FIG. 9 is a plan view of a snowmobile 100 and a rider 194. In FIG. 9,rider 194 is assuming a first riding posture. In a preferred embodimentof the present invention, a first moment is created about a pitch axisof snowmobile 100 when rider 194 assumes the first posture.

A snowmobile in accordance with the present invention may comprise aframe defining a tunnel, a track rotatably supported within the tunnel,and a seat fixed to the frame for receiving a rider. The snowmobile mayalso include a pair of handle bars rotatably coupled to the frame andadapted to receive the hands of a rider, and a pair of floor boardsfixed to the frame and adapted to receive the feet of the rider. Anengine of the snowmobile may be fixed to the frame and operativelycoupled to the track by a drivetrain. The snowmobile may have a pitchaxis extending laterally through a center of gravity thereof. In someembodiments of the present invention, the snowmobile may be configuredsuch that a first moment about the pitch axis is created when the riderassumes a first posture and a second moment about the pitch axis iscreated when the rider assumes a second posture. In some embodiments ofthe present invention, the first moment and the second moment may havedifferent directions.

In the embodiment of FIG. 9, snowmobile 100 includes a frame 124 and adrive 170. Drive 170 includes an engine 106 fixed to frame 124 and adrivetrain 120 operatively coupling engine 106 to a drive track 108. InFIG. 9, it may be appreciated that drive 170 includes an outer extent Ethat is disposed at a first radius R1 from a drive center axis extendinglaterally through snowmobile 100. In FIG. 9, it may also be appreciatedthat drive 170 is disposed within an imaginary cylinder CYL extendinglaterally through snowmobile 100.

With continuing reference to FIG. 9, it may be appreciated that acontrol point 160 of snowmobile 100 is disposed at a second radius R2from the axis of imaginary cylinder CYL. In the embodiment of FIG. 9,control point 160 is defined by a steering axis 168 and a grip plane162. In the embodiment of FIG. 9, a handlebar 150 rotates about steeringaxis 168. Grip plane 162 may be defined, for example, a first grip axisand a second grip axis. In some embodiments of the present invention,handlebar 150 may be moveable between a first position and a secondposition with steering axis 168 and grip plane 162 defining controlpoint 160 when handlebar 150 is in the first position, and with steeringaxis 168 and grip plane 162 defining second control point when handlebar150 is in the second position. A kneecap height KH of rider 194 isillustrated in FIG. 9. In certain embodiments of the present invention,first radius R1 is less than half of the kneecap height of apre-selected snowmobile rider. In some advantageous embodiments of thepresent invention, second radius R2 is greater than the kneecap heightof a pre-selected snowmobile rider

FIG. 10 is a plan view of a snowmobile 100 and a rider 194. In FIG. 10,rider 194 is assuming a second riding posture. In a preferred embodimentof the present invention, a second moment is created about a pitch axisof snowmobile 100 when rider 194 assumes the second posture.

FIG. 11 is a plan view of a snowmobile 100 and a rider 194. In theembodiment of FIG. 11, rider 194 is pulling backwardly on handlebar 150of snowmobile 100 with a first force 196A. Also in the embodiment ofFIG. 11, rider 194 is applying a generally forwardly directed secondforce 198B to toe stops 156 of snowmobile 100. The forces applied tosnowmobile 100 by rider 194 may create a third moment about the pitchaxis of snowmobile 100. In the embodiment of FIG. 11, a toe stop 156intersects a running board 154 of snowmobile 100 at an intersection 158.In FIG. 11 it may be appreciated that intersection 158 and a controlpoint 160 of snowmobile 100 are separated from one another by a distanceD. In FIG. 11, distance D1 is measured along a plane P1 that intersectscontrol point 160 and intersection 158. In some embodiments of thepresent invention, distance D1 is greater than a crotch height of apre-selected rider.

FIG. 12 is a plan view of a snowmobile 100 and a rider 194. In theembodiment of FIG. 12, rider 194 is assuming a forward leaning posture.Rider 194 may assume the forward leaning posture of FIG. 12, forexample, to control the attitude of snowmobile 100. In FIG. 12, it maybe appreciated that running boards 154 of snowmobile 100 and controlpoint 160 of snowmobile 100 are separated by a distance D2. In FIG. 12,distance D2 is measured along a plane P2 that intersects control point160 and is normal to a surface 200 of running boards 154. A crotchheight CH of rider 194 is illustrated in FIG. 12. In some embodiments ofthe present invention, distance D2 is greater than a crotch height of apre-selected rider.

FIG. 13 is a perspective view of an assembly in accordance with anexemplary embodiment of the present invention. The assembly of FIG. 13includes an engine 106 that is coupled to a frame 124 defining a tunnel122. Engine 106 is preferably operatively coupled to a drive track forpropelling a snowmobile in accordance with the present invention. Engine106 includes a cylinder block 136 defining a plurality of cylinder bores202 each having a cylinder bore axis 166.

Cylinder block 136 of engine 106 also defines a plurality of inlet ports204 and a plurality of exhaust ports 206. In the embodiment of FIG. 13,air enters engine 106 through inlet ports 204 and exhaust gases exitengine 106 via exhaust ports 206. In FIG. 13 it may be appreciated thatinlet ports 204 and exhaust ports 206 are both disposed on the same sideof a plane defined by the cylinder bore axes 166 of engine 106. In FIG.13, a plurality of exhaust pipes 220 are shown extending away fromengine 106. Each exhaust pipe preferably fluidly communicates with anexhaust port 206 of engine 106. The assembly of FIG. 13 also includes aplurality of throttle bodies 126. Each throttle body 126 preferablyfluidly communicates with an inlet port 204 engine 106. In FIG. 13 itmay be appreciated that engine 106 is generally disposed at an anglerelative to vertical so that cylinder bore axes 166 of engine 106 extendgenerally upwardly and rearwardly.

FIG. 14 is a perspective view of an assembly in accordance with anexemplary embodiment of the present invention. The assembly of FIG. 14comprises an engine 106 including a cylinder block 136 defining cylinderbores 202 having a cylinder bore axes 166. In the embodiment of FIG. 14,air enters cylinder bores 202 via throttle bodies 126 and inlet ports204. Exhaust gases may exit cylinder bores 202 via exhaust ports 206 andexhaust pipes 220 which fluidly communicate with exhaust ports 206.

In the embodiment of FIG. 14, air inlet ports 204 and exhaust ports 206are both disposed on a front side of engine 106. Also in the embodimentof FIG. 14, a heat shield 146 is disposed between air inlet ports 204and exhaust ports 206. In FIG. 14 it may be appreciated that heat shield146 extends between throttle bodies 126 and exhaust pipes 220.

FIG. 15 is a plan view of a snowmobile 100 in accordance with anexemplary embodiment of the present invention. In FIG. 15 it may beappreciated that snowmobile 100 includes an engine 106 that may beoperatively coupled to a drive track 108 for propelling snowmobile 100.In the embodiment of FIG. 15, drive track 108 of snowmobile 100 ispartially disposed within a tunnel 122 defined by a frame 124 ofsnowmobile 100.

In the embodiment of FIG. 15, a throttle body 126 is fluidly coupled toengine 106. Air entering engine 106 may flow through throttle body 126.Throttle body 126 is coupled to a chamber 224 defined by a lightweightshell 230. Filter media may be disposed within chamber 224 for filteringincoming air. Chamber 224 is fluidly coupled to an air plenum 130defined by a hood 132 of snowmobile 100.

In the embodiment of FIG. 15, air plenum 130 is configured such that airis drawn from an area proximate a rider's area 226 of snowmobile 100 anddirected to chamber 224. In FIG. 15, it may be appreciated that airplenum 130 communicates with an inlet 228 defined by a rear portion ofhood 132.

FIG. 16 is a plan view of a snowmobile 100 in accordance with thepresent invention. Snowmobile 100 of FIG. 16 includes a lightweightshell 230 defining a chamber 224. In the embodiment of FIG. 16 a hood132 of snowmobile 100 is rotatably coupled to lightweight shell 230 at ahinge 232. Hood 132 is preferably supported so that it can be movedbetween an open position and a closed position. In the embodiment ofFIG. 16, hood 132 is shown in the closed position.

In FIG. 16, it may be appreciated that when hood 132 is in the closedposition, chamber 224 communicates with a plenum 130 defined by hood132. Air may enter chamber 224 after traveling along an entrance path236 that extends along a longitudinal axis 222 of plenum 130. In theembodiment of FIG. 16, air exiting chamber 224 travels along an exitpath 238 extending through a conduit 240 and a throttle body 126. Athrottle body axis 234 of throttle body 126 is shown in FIG. 16. In theembodiment of FIG. 16, conduit 240 is disposed in a substantiallycoaxial arrangement with throttle body 126.

In FIG. 16, it may be appreciated that longitudinal axis 222 of plenum130 and throttle body axis 234 of throttle body 126 intersect to definean angle A. In the embodiment of FIG. 16, angle A is an acute angle.Embodiments of snowmobile 100 are possible in which longitudinal axis222 of plenum 130 and throttle body axis 234 of throttle body 126 aregenerally parallel to one another.

It is to be appreciated that hinge 232, the walls of lightweight shell230, and the walls of hood 132 are not necessarily drawn to scale inFIG. 16. For example, some of these elements may be depicted in arelatively enlarged manner for purposes of illustration. In FIG. 16 itmay be appreciated that of throttle body axis 234 intersects a cylinderbore axis 166 to define an angle B. Cylinder bore axis 166 extendsthrough a cylinder bore 138 defined by a cylinder block 136 of an engine106 of snowmobile 100. In the embodiment of FIG. 16, angle B is anobtuse angle.

Cylinder block 136 also defines an air inlet port 140 and an exhaustport 142. Air may enter a cylinder bore 138 of engine 106 via air plenum130, chamber 224, conduit 240, throttle body 126 and inlet port 144.Exhaust gases may exit cylinder bore 138 via exhaust port 142 and anexhaust pipe 148 which fluidly communicates with exhaust port 142. Inthe embodiment of FIG. 16, air inlet port 140 and exhaust port 142 areboth disposed on a front side 242 of engine 106.

In the embodiment of FIG. 16, hood 132 and shell 230 cooperate to form asnowmobile body 246. In the embodiment of FIG. 16, air enters plenum 130at a location proximate the rear of snowmobile body 246, then travels ina forward direction along entrance path 236 to an extreme front end ofsnowmobile body 246. The air then travels in a rearward direction alongexit path 238 toward engine 106. Entrance path 236 and exit path 238cooperate to form an air path 248. With reference to FIG. 16, it may beappreciated that air traveling through air path 248 travels a distancegreater than an overall length of hood 132. In some embodiments of thepresent invention, air traveling through air path 248 travels a distancegreater than an overall length of snowmobile body 246.

FIG. 17 is a perspective view of an assembly in accordance with anexemplary embodiment of the present invention. The assembly of FIG. 17includes an engine 106 that is coupled to a frame 124 defining a tunnel122. Engine 106 may be operatively coupled to a drive track forpropelling a snowmobile in accordance with the present invention. Engine106 includes a cylinder block 136 defining a plurality of cylinder bores202 each having a cylinder bore axis 166.

Cylinder block 136 of engine 106 also defines a plurality of inlet ports204 and a plurality of exhaust ports 206. In the embodiment of FIG. 17,air enters engine 106 through inlet ports 204 and exhaust gases exitengine 106 via exhaust ports 206. In FIG. 17 it may be appreciated thatinlet ports 204 and exhaust ports 206 are both disposed on the same sideof a plane defined by the cylinder bore axis 166 of engine 106. In FIG.17, a plurality of exhaust pipes 220 are shown extending away fromengine 106.

The assembly of FIG. 17 also includes a plurality of throttle bodies126. Each throttle body 126 preferably fluidly communicates with aninlet port 204 of engine 106. In FIG. 17 it may be appreciated thatengine 106 is generally disposed at an angle relative to vertical sothat each cylinder bore axis 166 of engine 106 extend generally upwardlyand rearwardly.

The assembly of FIG. 17 includes a conduit 240 that is shown extendingaway from throttle bodies 126. Conduit 240 defines a lumen 250 thatfluidly communicates with engine 106 via throttle bodies 126. In FIG.17, conduit 240 can be seen extending through an aperture 252 defined bya shock tower 254 of frame 124.

The assembly of FIG. 17 also includes a plurality of skis 256. Each ski256 is supported by a front suspension 260. In the embodiment of FIG.17, each front suspension 260 includes a plurality of suspension arms262. Each front suspension 260 also includes a spring assembly 258. Inthe embodiment of FIG. 17, each spring assembly 258 includes a shockabsorber 264 and a spring 266 that is disposed about shock absorber 264.It is to be appreciated that various embodiments of suspension arms 262are possible without deviating from the spirit and scope of the presentinvention. Examples of suspension arms which may be suitable in someapplications include A-arms and radius rods. In the embodiment of FIG.17, each ski 256 is preferably free to rotate about a ski axis 268.

FIG. 18 is a perspective view of an assembly including frame 124 of theprevious figure and a lightweight shell 230 that is preferably fixed toa front portion 268 of frame 124. In FIG. 18, it may be appreciated thatlightweight shell 230 defines a chamber 224 and an opening 270communicating with chamber 224. Opening 270 and chamber 224 preferablyalso communicate with engine 106 via a conduit 240 and a plurality ofthrottle bodies 126.

In FIG. 18 it may be appreciated that suspension arms 262 of frontsuspension 260 have been received within a plurality of channels 272defined by lightweight shell 230. In a preferred embodiment, channels272 are preferably dimensioned to receive suspension arms 262 ofsuspension 274.

FIG. 19 is a perspective view of an assembly including frame 124 andlightweight shell 230 shown in the previous figure. Additionally, theassembly of FIG. 19 includes a snowmobile hood 132 and a belly plate276. Hood 132, lightweight shell 230, and belly plate 276 cooperate toform a snowmobile body 246.

FIG. 20 is a cut away perspective view of an assembly includinglightweight shell 230 and hood 132 shown in the previous figure. In FIG.20, it may be appreciated that hood 132 comprises an outer wall 278 andan inner wall 280 defining a plenum 130. In FIG. 20 it may also beappreciated that lightweight shell 230 defines a chamber 224 fluidlycommunicating with plenum 130 defined by outer wall 278 and inner wall280 of hood 132.

FIG. 21 is a plan view of an assembly including a lightweight shell 230in accordance with an exemplary embodiment of the present invention. Inthe embodiment of FIG. 21, lightweight shell 230 is fixed to a frame 124by a plurality of fasteners 282. Lightweight shell 230 includes mountingholes dimensioned to receive a body portion of each fastener 284.Lightweight shell 230 also defines a plurality of notches 286dimensioned to receive a head portion of each fastener 284. In someembodiments, notches 286 are dimensioned to receive a tool which isadapted to engage the head portion of each fastener 284. Variousfasteners may be used without deviating from the spirit and scope of thepresent invention. Examples of fasteners which may be suitable in someapplications include threaded fasteners (e.g., screws) and rivets.

In FIG. 21, a conduit 240 is shown fixed to lightweight shell 230. Inthe embodiment of FIG. 21, conduit 240 and lightweight shell 230 arepreferably formed from a single piece of material. Conduit 240 andlightweight shell 230 may be formed, for example, from a polymericmaterial using a rotational molding process.

A cavity defined by lightweight shell 230 preferably communicates with athrottle body 126 via conduit 240. In FIG. 21, it may be appreciatedthat a flexible coupling 288 is interposed between conduit 240 andthrottle body 126. Flexible coupling 288 preferably acts to reduce thelevel of vibrations transmitted between throttle body 126 andlightweight shell 230. In some embodiments, flexible coupling 288 maycomprise an elastomeric material. In the embodiment of FIG. 21, flexiblecoupling 288 comprises a bellows 290 having a plurality of convolutions292.

Lightweight shell 230 includes a mounting flange 294 defining a hole296. In some embodiments, hole 296 is dimensioned to receive a pin forrotatably coupling a snowmobile hood to lightweight shell 230.Lightweight shell 230 also includes an outer surface 200. In theembodiment of FIG. 21, outer surface 200 has a generally curved shape.In some embodiments of the present invention, outer surface 200 may havea generally convex shape. A shell having a generally curved shape mayaid in gliding over deep snow.

FIG. 22 is a cross sectional view of an assembly including a lightweightshell 230 in accordance with an exemplary embodiment of the presentinvention. In the embodiment of FIG. 22; a hood 132 is rotatably coupledto lightweight shell 230 at a pin 298 so that hood 132 can be movedbetween an open position and a closed position. In the embodiment ofFIG. 22, hood 132 is in a closed position. Hood 132 and a frame 124define an engine compartment 300. Hood 132 may be moved to an openposition, for example, when it is desirable to gain access to an enginedisposed in engine compartment 300.

In the embodiment of FIG. 22, a chamber 224 defined by lightweight shell230 communicates with a throttle body 126 via a lumen 350 defined by aconduit 240. In FIG. 22, it may be appreciated that a flexible coupling288 is interposed between conduit 240 and throttle body 126. In theembodiment of FIG. 22, flexible coupling 288 comprises a bellows 290having a plurality of convolutions 292.

Hood 132 includes an inner wall 280 and an outer wall 278. The walls ofhood 132 define a plenum 130 which communicates with chamber 224 atleast When hood 132 is in the closed position shown in FIG. 22.

FIG. 23 is an additional cross sectional view of the assembly of theprevious figure. In the embodiment of FIG. 23, hood 132 is disposed inan open position. In FIG. 23, it may be appreciated that chamber 224defined by lightweight shell 230 may be accessed through an opening 270when hood 132 is in the open position.

FIG. 24 is a plan view of snowmobile 100. In FIG. 24 it may beappreciated that snowmobile 100 includes a fuel tank 302 having a fueltank center of gravity CGE. In the embodiment of FIG. 24, fuel tankcenter of gravity CGE is disposed at a first radius RE relative tocenter of gravity CG of snowmobile 100.

In FIG. 24 a different fuel tank 302 is illustrated using dashed lines.Different fuel tank 302 has a different fuel tank center of gravity CGF.In FIG. 24 it may be appreciated that different fuel tank center ofgravity CGF lies at a second radius RF relative to center of gravity CGof snowmobile 100. In the embodiment of FIG. 24, radius RF is greaterthan radius RE, thus snowmobile 100 would have a greater polar moment ofinertia if fuel tank 302E was replaced with different fuel tank 302F.

In the embodiment of FIG. 24, engine 106 and fuel tank 302E are bothpositioned proximate center of gravity CG of snowmobile 100 providing arelatively small polar moment of inertia (PMI). In FIG. 24, it may beappreciated that a front wall 364 of fuel tank 302E is disposedproximate engine 106.

FIG. 25 is a perspective view of a handle bar assembly including ahandlebar 550 that is coupled to a shaft 584. A steering axis 568 isshown in FIG. 25. A snowmobile in accordance with an exemplaryembodiment of the present invention may include handlebar 550 and shaft584. This snowmobile may be configured so that handlebar 550 and shaft584 rotate about steering axis 568. Handle bar 550 includes a first gripportion and a second grip portion. A first grip axis 586 and a secondgrip axis 588 are shown in FIG. 25. First grip axis 586 and second gripaxis 588 define a grip plane 562. A control point 560 is disposed at thepoint where steering axis 568 intersects grip plane 562.

Handle bar 550 may form a portion of the human-to-machine interface of asnowmobile in accordance with an exemplary embodiment of the presentinvention. This human-to-machine interface may also include, forexample, a seat, a pair of running boards, and a pair of toe stops. Theoperator of such a snowmobile may control the snowmobile by applyingforces to handlebar 550, the seat, the running boards, and the toestops. The operator of the snowmobile may also control the snowmobile byassuming various postures in which the operators weight is distributedover handlebar 550, the running boards, the toe stops, and the seat invarying degrees.

In some exemplary embodiments of the present invention, a toe stopintersects a running board at an intersection. In these exemplaryembodiments, control point 560 may be disposed at a pre-selecteddistance from the intersection. In certain embodiments, the distancebetween control point 160 and the intersection may be greater than acrotch height of a pre-selected rider. Measurements from variouspre-selected riders may be used without deviating from the spirit andscope of the present invention. Examples of pre-selected riders that maybe suitable in some applications include an average snowmobilepurchaser, a 5^(th) percentile female from anthropometric data, and a95^(th) percentile male from anthropometric data.

Anthropometric data from various sources may be utilized withoutdeviating from the spirit and scope of the present invention. Oneexemplary source of anthropometric data is MIL-STD-1472C. FIG. 26 is atable of standing body dimensions that appears in MIL-STD-1472C. FIG. 27is an illustration of standing body dimensions that corresponds to thetable in FIG. 26. The illustration in FIG. 27 may also be found inMIL-STD-1472C.

Several forms of invention have been shown and described, and otherforms will now be apparent to those skilled in art. It will beunderstood that embodiments shown in drawings and described above aremerely for illustrative purposes, and are not intended to limit thescope of invention defined claims which follow.

1. A snowmobile comprising: a chassis; at least one ski coupled to the chassis by a suspension so that the ski is pivotable about a steering axis; a shell defining a chamber fluidly communicating with an engine of the snowmobile; the shell fixed to a front portion the chassis and extending away from the chassis in a forward direction; and wherein the shell is disposed forward of the steering axis.
 2. The snowmobile of claim 1, wherein the shell defines a plurality of channels.
 3. The snowmobile of claim 2, wherein at least one of the channels is dimensioned to accept a control arm of the suspension.
 4. The snowmobile of claim 1, further including a hood rotatably supported by the shell.
 5. The snowmobile of claim 4, wherein the shell has sufficient ridgity to support the weight of the hood when the hood is in an open position.
 6. The snowmobile of claim 1, wherein the shell has sufficient flexibility to deflect during a collision for absorbing energy from the collision and for decelerating the snowmobile in a controlled fashion so as to protect the rider from rapid deceleration.
 7. The snowmobile of claim 1, where the chassis includes a shock tower defining an aperture sized to receive a conduit fluidly communicating with a chamber defined by the shell.
 8. The snowmobile of claim 1, wherein the shell includes a generally curved outer surface for gliding over deep snow.
 9. The snowmobile of claim 8, wherein the generally curved outer surface comprises a generally convex surface.
 10. A snowmobile comprising: a chassis; a shell fixed to a front portion the chassis and extending away from the chassis in a forward direction; a hood rotatably supported by the shell; the shell defining a chamber fluidly communicating with an engine of the snowmobile; the hood including an outer wall and an inner wall; the walls of the hood defining a plenum; and the plenum fluidly communicating with the chamber defined by the shell at least when the hood is in a closed position.
 11. The snowmobile of claim 10, wherein the chamber defined by the shell may be accessed via an opening in the shell when the hood is in an open position.
 12. The snowmobile of claim 10, wherein a longitudinal axis of the plenum and a longitudinal axis of a throttle body of the snowmobile are generally parallel to one another.
 13. The snowmobile of claim 10, wherein a longitudinal axis of the plenum and a longitudinal axis of a throttle body of the snowmobile intersect to define an angle.
 14. The snowmobile of claim 13, wherein the angle is an acute angle.
 15. The snowmobile of claim 10, wherein air enters the engine via an air flow path extending through the plenum and the chamber; and wherein the air flow path has a length greater than a length of the hood of the snowmobile.
 16. The snowmobile of claim 10, further including a flexible coupling interposed between the shell and the engine.
 17. The snowmobile of claim 16, wherein the flexible coupling comprises an elastomeric material.
 18. The snowmobile of claim 16, wherein the flexible coupling comprises a plurality of convolutions.
 19. The snowmobile of claim 16, wherein the flexible coupling comprises a bellows.
 20. The snowmobile of claim 10, further comprising at least one ski coupled to the chassis by a suspension such that the ski is rotatable about a steering axis; and wherein the shell is disposed forward of the steering axis.
 21. The snowmobile of claim 10, wherein the plenum communicates with an inlet disposed proximate a rider area of the snowmobile.
 22. The snowmobile of claim 10, wherein the shell has sufficient rigidity to support the weight of a hood of the snowmobile when the hood is in an open position.
 23. The snowmobile of claim 10, where the chassis includes a shock tower defining an aperture sized to receive a conduit fluidly communicating with the chamber of the shell.
 24. The snowmobile of claim 10, wherein the shell includes a generally curved outer surface for gliding over deep snow.
 25. The snowmobile of claim 24, wherein the generally curved outer surface comprises a generally convex surface.
 26. A snowmobile comprising: a chassis; a shell fixed to a front portion the chassis and extending away from the chassis in a forward direction; an engine coupled to the chassis for propelling the snowmobile; and the shell defining a chamber fluidly communicating with the engine via a flexible coupling interposed between the shell and the engine.
 27. The snowmobile of claim 26, further including a hood having an outer wall and an inner wall; and the walls of the hood defining a plenum communicating with the chamber.
 28. The snowmobile of claim 27, wherein a longitudinal axis of the plenum and a longitudinal axis of a throttle body of the snowmobile are generally parallel to one another.
 29. The snowmobile of claim 27, wherein a longitudinal axis of the plenum and a longitudinal axis of a throttle body of the snowmobile intersect to define an angle.
 30. The snowmobile of claim 29, wherein the angle is an acute angle.
 31. The snowmobile of claim 26, wherein air enters the engine via an air flow path extending through the plenum and the chamber; and wherein the air flow path has a length greater than a length of the hood of the snowmobile.
 32. The snowmobile of claim 26, wherein the plenum communicates with an inlet disposed proximate a rider area of the snowmobile.
 33. The snowmobile of claim 26, where the chassis includes a shock tower defining an aperture sized to receive a conduit fluidly communicating with the chamber of the shell.
 34. The snowmobile of claim 26, wherein the shell includes a generally curved outer surface for gliding over deep snow.
 35. The snowmobile of claim 34, wherein the generally curved outer surface comprises a generally convex surface. 